IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308 _______________________________________________________________________________________ Volume: 04 Issue: 05 | May-2015, Available @ http://www.ijret.org 340 A STUDY ON SEISMIC PERFORMANCE OF HIGH RISE IRREGULAR RC FRAMED BUILDINGS S Monish 1 , S Karuna 2 1 Post Graduate Student, Department of civil engineering, The oxford college of engineering 2 Assistant Professor, Department of civil engineering, The oxford college of engineering Abstract Earthquakes are known as one of the most unpredictable and devastating of all natural disasters, however the unpredictable nature of occurrence of these earthquakes makes it difficult to prevent loss of human lives and destruction of properties, if the structures are not designed to resist such earthquake forces. In this paper attempt has been made to study two types of plan irregularities namely diaphragm discontinuity and re-entrant corners in the frame structure. These irregularities are created as per clause 7.1 of IS 1893:2002(part1) code. Various irregular models were considered having diaphragm discontinuity and re- entrant corners which were analysed using ETABS to determine the seismic response of the building. The models were analysed using static and dynamic methods, parameters considered being displacement, base shear and fundamental natural period. From the present study the model which is most susceptible to failure under very severe seismic zone is found, modelling and analysis is carried out using ETABS. Keywords: Diaphragm, re-entrant, static, dynamic. --------------------------------------------------------------------***------------------------------------------------------------------ 1. INTRODUCTION Our world is facing a threat of natural disasters from time to time. Earthquakes are one of the most unpredictable and devastating of all natural disasters. The records based on earthquakes occurrence show that the consequences are loss of human lives and destruction of properties which eventually affects the national economy. However the occurrence of earthquakes cannot be predicted and prevented but we can design the structures to resist such earthquake forces. For a structure to perform well in earthquake, the structure should possess four main attributes, namely simple and regular configuration, adequate lateral strength, stiffness and ductility. Structures with simple regular geometry and uniformly distributed mass and stiffness in plan as well as in elevation are considered to suffer much lesser damage than structures with irregular configurations. But nowadays, with the advancement in rapid growth of urbanization and for aesthetic purpose buildings with irregular structural configurations are widely constructed. These configurations in buildings leads to non-uniform distributions in their masses, stiffness and strength therefore they are prone to damage during earthquakes. Hence in present study an attempt has been made to study the behaviour of such structures located in severe seismic zone. The section 7 of IS 1893(part1):2002 enlists the irregularity in buildings. These irregularities are categorised as follows [11] 1. Vertical irregularities referring to sudden change of strength, stiffness, geometry and mass results in irregular distribution of forces or distribution over the height of the building. 2. Plan irregularities which refer to asymmetrical plan shapes(L-,T-,U-,F-) or discontinuities in the horizontal resting elements (diaphragms) such as cut-outs, large openings, re-entrant corners and other abrupt changes resulting in torsion, diaphragm deformations and stress concentration. As mentioned above plan irregularities may be due to diaphragm discontinuity or presence of re-entrant corners in the buildings. The diaphragm is a horizontal element that transfers forces between vertical resistance elements. The diaphragm discontinuity may occur with abrupt variations in stiffness, including those having cut-out or open areas greater than 50% of the gross enclosed diaphragm area, or change in effective diaphragm stiffness of more than 50% from one storey to the next storey. The re-entrant corners, where projections of the structure beyond the re-entrant corner are greater than 15 percent of its plan dimension in the given direction is assumed in shapes like L, T, H, C, + shapes 1.1 Objective of study To study the effect of plan irregularity i.e. diaphragm discontinuity and re-entrant corners in high rise buildings under severe seismic zone considering parameters like displacement, fundamental natural period and base shear. 1.2 Methodology The method of analysis used for the present study are 1. Equivalent static method 2. Response spectrum method
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A study on seismic performance of high rise irregular rc framed buildings
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IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308
Volume: 04 Issue: 05 | May-2015, Available @ http://www.ijret.org 340
A STUDY ON SEISMIC PERFORMANCE OF HIGH RISE IRREGULAR
RC FRAMED BUILDINGS
S Monish1, S Karuna
2
1Post Graduate Student, Department of civil engineering, The oxford college of engineering
2Assistant Professor, Department of civil engineering, The oxford college of engineering
Abstract Earthquakes are known as one of the most unpredictable and devastating of all natural disasters, however the unpredictable
nature of occurrence of these earthquakes makes it difficult to prevent loss of human lives and destruction of properties, if the
structures are not designed to resist such earthquake forces. In this paper attempt has been made to study two types of plan
irregularities namely diaphragm discontinuity and re-entrant corners in the frame structure. These irregularities are created as
per clause 7.1 of IS 1893:2002(part1) code. Various irregular models were considered having diaphragm discontinuity and re-entrant corners which were analysed using ETABS to determine the seismic response of the building. The models were analysed
using static and dynamic methods, parameters considered being displacement, base shear and fundamental natural period. From
the present study the model which is most susceptible to failure under very severe seismic zone is found, modelling and analysis is